Rotary switches or rotary variable resistors (these components will be collectively referred to as rotary operation type electronic components) used, for example, in portable electronic devices may be operated by a gloved hand or in an environment where it is difficult to work with precision. Those portable electronic devices are accordingly required to have rotary operation type electronic components having a large rotary-operation knob for easier operation. The larger the operation knob becomes, however, the more the operation torque is applied to the control shaft. Therefore, an erroneous operation is likely to happen if the operation knob is turned excessively, or is turned unintentionally due to an unexpected force from the outside or when the operator is startled by a sudden sound or light. Rotary operation type electronic components reduced in size for miniaturized portable electronic devices have naturally reduced the operation torque required for rotary operation and have the problem of increasing the possibility of similar erroneous operation. Accordingly, a rotary operation type electronic component that requires a large torque for the turning operation is proposed in Patent literature 1.
FIG. 1 shows a sectional view of the rotary operation type electronic component disclosed in Patent literature 1, in which a thin resilient metal sheet 300 folded into a polygon (hereafter referred to as a polygonal leaf spring) is placed between the inner periphery of a through shaft hole 100a formed in a shaft supporter 100 and the outer periphery of a control shaft 200 inserted into the through shaft hole 100a. The polygonal leaf spring 300 is held in such a bent state that the center of each folded side is pressed radially outward by the outer periphery of the control shaft 200. When the control shaft 200 is going to be turned, a sliding frictional force is generated between the leaf spring 300 and the control shaft 200 and an amount of torque corresponding thereto is needed for the turning operation. By placing such a type of polygonal leaf spring 300 to increase the torque needed for the turning operation, the possibility of erroneous operation can be reduced.